Lubricating grease and method of making the same



United" States Patent 3,211,650 LUBRICATING GREASE AND METHOD OF MAKING THE SAME Leon M. Oswalt, Oklahoma City, Okla., assignor to Cato Oil and Grease Company, Inc., a corporation of Oklahoma No Drawing. Filed Mar. 15, 1962, Ser. No. 180,030

18 Claims. (CL 252-39) The present invention relates to lubricating greases and methods for making the same, more particularly to anhydrous calcium greases that are characterized by good adhesive qualities, that is, that are capable of sticking closely to metal surfaces in motion even under sudden shock. The invention is more particularly concerned with such greases and methods involving the use of polymerization products the addition of which produces flattened temperature-viscosity curves in comparison to greases free from such polymerization products and which therefore have the advantage that even at low temperatures the power losses due to internal friction of the lubricant are only slightly higher than at normal temperatures.

As is well known, greases of this type are mixtures of lime soaps and mineral oil; and although it may not be quite accurate to refer to them as gels, nevertheless, the grease structure is quite analogous to the structure of a gel in that the soap forms a matrix or framework within which the oil is retained. conventionally, saponification of the fatty acid or other fatty compound takes place after admixture with the hydrocarbon oil, the lime soap forming as fibers which comprise the gelling matrix referred to above. The properties of the grease are therefore dependent in large degree on the properties and arrangement of these fibers. For one thing, the mechanical stability of the grease seems to be influenced by the length to diameter ratio of the fibers. For another thing, the capillary attraction of the fibers for the oil varies inversely as the diameter of the fibers. If the capillary attraction is too low, bleeding may take place. Bleeding is a phenomenon in which oil separates from the grease upon standing. On the other hand, if the fibers are too fine, then the grease has little body and may even tend to flow under its own weight. Also, difficulty is encountered from chemical instability in that greases tend to oxidize; and further difiiculty is encountered from lumpiness, that is, the tendency of the grease as formulated to have non-uniform consistency characterized by lumps.

It will be seen, therefore, that the technique of producing greases having the desired mechanical properties is an art, not a science, and depends on a number of factors which cannot be precisely correlated. Among these factors are the chemical identity of the fatty compound, the chemical identity of the cation donor, the heat treatment during and after saponification, the nature of the hydrocarbon oil, and the proportions of the ingredients at various stages of compounding.

Further complications are introduced by the use of polymerization products as described above. Although the mechanism by which these polymerization products decrease the over-all effect of temperature on viscosity, thereby increasing the viscosity index, is not known with certainty, it is likely that they achieve this because they are relatively long, slender molecules that tend to ball up at low temperature and thus offer little resistance to flow, but straighten out at high temperature thereby impeding flow and increasing the viscosity, with the overall result that the viscosity of the grease as a whole changes relatively little with temperature. In any event, however, it is obvious that the incorporation of such products in a grease adds further difiiculties to the attempt to produce greases having desirable characteristics,

for the use of such polymerized additives inevitably changes the gel structure or soap matrix of the grease.

Although many attempts have been made to overcome the above and other difficulties and disadvantages in this field, none, as far as is known, has been entirely successful when practiced industrially on a commercial scale.

Accordingly, it is an object of the present invention to provide lubricating greases and methods for making the same which will have markedly improved shear stability, substantially no bleeding, improved adhesion to bearing surfaces, greatly improved susceptibility to treatment by agents designed to improve the chemical stability and to improve the properties under extreme pressure, improved leak resistance and cushioning effect, and freedom from lumpiness.

It is also an object of the invention to provide a lubrieating grease and method of making the same that requires less soap to achieve the desired characteristics.

Finally, it is an object of the present invention to provide lubricating greases and methods for making the same which will be simple and inexpensive to manufacture and rugged and durable in use.

Other objects and advantages of the present invention will become apparent from a consideration of the following description.

Broadly stated, the present invention comprises the discovery that lubricating greases having properties achieving the above objects of the invention can be produced by employing certain material Within certain ranges of operating conditions. More particularly, it has been discovered that a grease achieving the above objects is produced when hydroxy stearic acid is saponified with lime in a medium of naphthenic oil which at F. has a viscosity of about 90420 SUS and a viscosity index from below zero to about 50, and if there is thereafter admixed with the resulting soap and oil a polymerization product comprising polyisobutylene having an average molecular weight of about l7,50018,500. Preferably, the lime and hydroxy stearic acid are present at the beginning of saponification in an amount which together is equal in weight to about 2838% of the weight of the mixture at the beginning of saponification. It is also preferable that substantially all the Water present at the beginning of saponification be in combination with the lime, preferably in the fonm of calcium hydroxide. saponification is preferably conducted at about 250 F., and the completed soap should be essentially free from glycerine. After saponification, the material is quenched to about 230 F. by addition of further oil. The material is then slowly cooled during addition of the polyisobutylene. The amount of polyisobutylene should preferably be about 812% by weight of the whole.

In more detail, the lime employed can be in any of the forms usually employed in grease manufacture with the proviso that there should be some water present in combination with the lime. Thus, the lime can include calcium oxide, calcium hydroxide, or other reactive calcium compound, so long as there is at least some combined water present, as in calcium hydroxide. If desired, all the lime can be in the form of calcium hydroxide. In this way, there is sllfficient water present to begin the reaction but no more water than is necessary, so that no Water need be boiled off during or after saponification and no water remains in emulsified form in the grease. A truly anhydrous grease is thus produced, and there need be no temperature rise at the end of saponification.

The hydroxy stearic acid can also take a variey of forms, such as 9 hydroxy stearic acid, 9,10 dihydroxy stearic acid, and the like; but the preferred fatty component is 12 hydroxy stearic acid.

The oil base which is at least initially present during formulation of the grease, known in this art as the cooking oil, is a highly aromatic or naphthenic base such as those obtained from Venezuelan, Colombian, or Gulf Coastal crudes and also to some extent from central Arkansas and some fields in California. Naphthenic lube oil according to the present invention is produced in the usual manner from naphthenic crudes, by distilling off the gasoline and then treating in a vacuum tower from which the overhead of relatively low viscosity is the distillate lube stock which can then for example be acid treated with sulfuric acid to produce an acid sludge which is then removed. In its preferred embodiments, the cooking oil has a viscosity index of about -30, a gravity of about 20-25 API at 60 F., a pour point of about --10 to '70 F., and more preferably about -30 to 60 F., an ASTM color of less than 2, and a flash point of about 300-350 F. The use of naphthenic lube stock as the cooking oil results in improved crystal formation, better mechanical stability, and also in a better yield in terms of the amount of soap necessary to produce a given cons'istency of grease, so that when naphthenic oil is used as the cooking oil, within the viscosity range of 90-120 SUS and the viscosity index range of below zero to about 50, less soap is necessary to produce a given consistency of grease.

Preferably, the fatty compound is melted and then mixed with about twice its weight of naphthenic oil at about the same temperature, although the fatty compound and oil may be premixed prior to melting the fatty compound. The lime is then slurried in a premix vessel with somewhat more than its weight in oil and the slurry is added to the other mixture and the temperature then raised to a saponification temperature of about 250 F. Saponification may proceed for about five hours.

At the end of saponification, the oil is quenched over a relatively small temperature range. Specifically, the saponified material is reduced in temperature by about 20 from about 250 to about 230 in not more than about five minutes, preferably about four minutes. Preferably, this is done stepwise, as in two steps of two minutes each with five to ten minutes stirring between. Quenching is effected by adding a reduction oil, that is, an oil that somewhat dilutes the soap. This oil may be the same as the cooking oil.

This short quench in the neighborhood of the recited temperature range largely determines the characteristics of the soap fibers. Subsequent cooling has considerably lessinfluence on the fiber structure than does the quench. The freedom from lumpiness that is achieved in the present invention is due in part to the choice of a cooking oil and in part to the subsequent new treatment.

The polyisobutylene may then be introduced, preferbly in an oil solution. The oil solution of polyisobutylene may be added slowly to the previous material with mixing. If the oil solution of polyisobutylene is held at a little above room temperature to improve its pour characteristics, then its slow addition over a period of several hours will slowly reduce the temperature of the grease so as to achieve slow cooling of the grease.

As stated, the polyisobutylene has an average molecular weight about 17,50018,500 as measured by the Staudinger method described in Die Hochmolekularen Organischem Verbindungen, H. Staudinger, Berlin, 1932, Verlag von Julius Stringer, page 56. It may be present as a minor proportion in a solvent which could for example be solventextracted Mid-Continent stock which could have a variety of viscosities, preferably about 190- 220 SUS at 100 F., and high viscosity index, that is, 95 or above. If the polyisobutylene is only a minor proportion of the material in which it is dissolved, then the quantity of polyisobutylene solution added after reduction of the soap will very likely be greater than the material to which it is added.

Other materials may then be added to the grease, such as extreme pressure lubricating agents, oxidation inhibitors, pour inhibitors, dyes, colloidal metals, graphite, mica, talc, soapstone, whiting and other cushioning agents or natural lubricants and the like, by stirring into the mixture previously formed.

The grease may then be milled, deaerated, packaged, et cetera. The finished grease is ideally suited for gun application, as in the lubrication of chassis, spring shackles, traveling cranes, cams, textile machinery and other equipment requiring a highly adhesive grease not subject to being thrown out by centrifugal force and not subject to spattering.

Greases thus compounded have considerably improved properties as compared to greases known heretofore. In the first place, they have extremely high mechnical stability. In terms of the standard ASTM penetration test, such greases may have a penetration in the range 265- 295, both unworked and as worked 60 strokes. But after 100,000 strokes, such greases have an increase of only about 15-30 in their penetration, while prior art greases are ordinarily fully liquid after 100,000 strokes.

In the second place, such greases have extremely good susceptibility to agents designed to improve the chemical stability, as indicated by greatly reduced oxidation. In the standard ASTM oxidation bomb test, such greases will bring about a pressure drop of only 4-6 p.s.i. during 500 hours at 210 F.; while greases according to the prior art are considered to be very good if they bring about this pressure drop in hours.

Moreover, the susceptibility to the action of agents designed to improve the extreme pressure properties of such greases is greatly improved. As measured by the Timken extreme pressure test, such greases will take a 50-pound load; while by contrast, only a 10-pound load is typical of'prior art greases, a 30-35-pound load tolerance being obtainable by the use of a lead-soap grease. Lubricating greases according to the present invention are also characterized by improvements in the other properties mentioned toward the beginning of this specification.

To enable those skilled in this art to practice the invention, the following illustrative example is given:

Example an ASTM color of 1.5, and a gravity of 23.5 API at 60 F. The mixture is stirred throughout the addition and the temperature is maintained at F. In a separate premix vessel, 1.56 parts by weight of calcium hydroxide and 2.3 parts by weight of the naphthenic oil described above are slurried and added to the steam-heated reaction Vessel while stirring while maintaining the temperature at 180 F. p The temperature of the steam-heated vessel is then raised to 250 F. and maintained at that temperature for five hours with stirring. The steam input is then cut off; and with continued stirring, another 7.65 parts by weight of the naphthenic oil described above are added.

to the reaction product in the kettle in two equal parts,

thereby to quench and reduce the soap. Each part of reduction oil is added to the batch with stirring, two

1 minutes being required for each addition and the batch being stirred for ten minutes between the two additions. The temperature drops upon the first addition from 250 F. to 240 F. and upon the second addition from 240, F. to 230 P. Then 75 parts by weight of an oil solution containing 20% by volume of a linear polymer of polyisobutylene having an average molecular weight of 18,000

are added to the soap-oil solution in the kettle gradually with continued stirring. The oil in which the polyisobutylene is dissolved is a solvent-extracted mid-Continent stock having a viscosity of 200 SUS at 100 F. and a viscosity index of 100. The polyisobutylene solution is at a temperature of 110 F. and is continuously added to the batch with stirring. The addition takes two hours, at the end of which time the temperature of the batch is 150 F. There are then added 3 parts by weight of a 50% oil solution of lead diamyldithiocarbamate and 0.6 part by weight of a 50% oil solution of zinc diamyldithiocarbamate as antioxidant and extreme pressure lubricating agents. After milling and deaeration, the grease has an unworked penetration of 280, a 60 stroke worked penetration of 280 (ASTM test D217-52T), a 100,000 stroke worked penetration of 295, an NLGI consistency of No. 2 grade, a grease oxidation bomb test of 5 p.s.i. drop during 500 hours at 210 F. (ASTM D-942), a water content of 0.0, and a Timken extreme pressure test of 50- pound O.K. load. At the end of two weeks, there is no evidence of bleeding.

Although the present invention has been described in connection with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

What is claimed is:

1. A method of making an adhesive lubricating grease, comprising saponifying hydroxy stearic acid with lime in a naphthenic cooking oil which at 100 F. has a viscosity of about 90-120 SUS and a viscosity index from below zero to about 50, and thereafter admixing with the resulting soap and oil about 812% by weight of linear polyisobutylene having an average molecular weight of about 17,500-18,500.

2. A method as claimed in claim 1, in which the lime and hydroxy stearic acid present at the beginning of saponification are together equal in weight to about 28- 38% of the weight of the mixture at the beginning of saponification.

3. A method as claimed in claim 1, in which substantially all the water present at the beginning of saponification is in combination with the lime in the form of calcium hydroxide.

4. A method as claimed in claim 1, in which the saponification is conducted at about 250 F.

5. A method as claimed in claim 4, in which the saponified material is quenched from said temperature of about 250 F. to about 230 F.

6. A method as claimed in claim 1, in which the linear polyisobutylene is about 12% by Weight of the grease.

7. A method as claimed in claim 1, in which the viscosity index of the cooking oil is about -30.

8. A method as claimed in claim 1, in which the pour point of the cooking oil is about 10 to F.

9. A method as claimed in claim 1, in which the pour point of the cooking oil is about 30 to 60 F.

10. A lubricating grease made by the method of claim 1.

11. A method of making an adhesive lubricating grease, comprising saponifying hydroxy stearic acid with lime in a naphthenic cooking oil which at 100 F. has a viscosity of about -120 SUS, a viscosity index of about l030 and a pour point of about 30 to 60 F., saponification proceeding at a temperature of about 250 F. for about five hours, the lime and hydroxy stearic acid present at the beginning of saponification together being equal in weight to about 2838% of the weight of the mixture at the beginning of saponification, substantially all the water present at the beginning of saponification being in combination with the lime in the form of calcium hydroxide, quenching the saponified material from a temperature of about 250 F. to about 230 F. in not more than about five minutes by the addition of oil to the saponified material, and thereafter admixing with the resulting soap and oil about 812% by weight of linear polyisobutylene having an average molecular weight of about l7,500l8,500.

12. A method as claimed in claim 11, in which the linear polyisobutylene is about 12% by weight of the grease.

13. A method as claimed in claim 5, in which the quenching is performed in not more than about 5 minutes.

14. A method as claimed in claim 5, in which the quenching is performed in a plurality of steps with stirring between the quenching steps.

15. A method as claimed in claim 14, the quenching steps totalling not more than about 5 minutes in length.

16. A method as claimed in claim 1, in which the cooking oil has a gravity of about 20-25 API at 60 F., an ASTM color of less than 2, and a flash point of about 300350 F.

17. A method as claimed in claim 11, in which the quenching is performed in a plurality of steps.

18. A lubricating grease made by the method of claim 12.

References Cited by the Examiner UNITED STATES PATENTS 2,062,346 12/36 Zimmer et al. 25239 2,607,734 8/52 Sproule et al. 25239 2,758,981 8/56 Cooke et al. 25239 2,940,931 6/60 Nelson 25239 2,947,696 8/60 Nelson 25239 DANIEL E. WYMAN, Primary Examiner.

JOSEPH R. LIBERMAN, Examiner. 

1. A METHOD OF MAKING AN ADHESIVE LUBRICATING GREASE, COMPRISING SAPONIFYING HYDROXY STEARIC ACID WITH LIME IN A NAPHTHENIC COOKING OIL WHICH AT 100*F. HAS A VISCOSITY OF ABOUT 90-120 SUS AND A VISCOSITY INDEX FROM BELOW ZERO TO ABOUT 50, AND THEREAFTER ADMIXING WITH THE RESULTING SOAP AND OIL ABOUT 8-12% BY WEIGHT OF LINEAR POLYISOBUTYLENE HAVING AN AVERAGE MOLECULAR WEIGHT OF ABOUT 17,500-18,500. 